150 patients beginning fluindione treatment (or resuming after 2 weeks rest) will be recruited in the following departments: Geriatric, Cardiology, Nephrology, Cardiac Surgery, Internal Medicine (CHU Bichat-Claude Bernard, Paris) and Metabolic Diseases and Internal Medicine (CHU d'Angers). Blood sampling will take place before the beginning of the study (J0) to measure baseline INR and coagulation factors II and VII. Fluindione concentrations will also be measured in non-naive patients. INR, coagulation factors and fluindione will be measured at J2, J4, J6, J8, and twice weekly until they leave the hospital or up to a month. Many covariates will be recorded: age, gender, concurrent medications, biochemical analyses, functional and nutritional status. We will also investigate genetic factors by collecting DNA to genotype polymorphisms related to the target of the drug. Recent work has shown that both the response to common anticoagulant drugs and their metabolism was influenced by genetic polymorphisms, and there is now convincing evidence that drug targets are controlled by genetic polymorphisms which can play a major role in the variability of the response.